Recycling Ambient Wi-Fi Signals for Low Energy Wake-Up of Wireless Sensors

In this letter, waking-up wireless sensors is achieved by solely relying on existing ambient radio frequency signals from commercial Wi-Fi routers. The wake-up is accomplished based on the captured Wi-Fi signal that is received by an antenna and then fed into a rectifier circuit. A novel packet injection algorithm is developed to enable the rectifier to efficiently convert the captured Wi-Fi signal into a dc power. This algorithm can be implemented on any commercial router with no modifications to the router's hardware or protocol stack and without compromising the performance of the Wi-Fi network. The design is experimentally validated under controlled conditions.